Semi-transparent solar panels allow concurrent production of crops and power • Hacker News Board

Re: Semi-transparent solar panels allow concurrent production of crops and power

#121

Post by carvink » Sun, Aug 23, 2020, 7:17 PM UTC

dghughes wrote: post #85

My mother ayed tomatoes in the spring when it was still cool. She covered them with clear plastic bags as she always has. But she needed one more bag so she used a blue recycling bag on one of the plants. Blue tinged really it's almost clear. I pointed out to her one of the plants had yellow leaves. It was the plant with the blue bag. Later in the summer the blue bag plant produced fruit just like the other plants. B…

That slight colour blockage, or the tint those solar panels have is helpful.

There are two reasons. One, plants grow better under red light. Red light has the highest efficiency for photosynthesis in plants, that why LED grow lights are tuned for certain wavelengths. Plants use blue light to know what direction to grow.

And for a certain category of tints or dyes that are fluorescent, additional red light.

Luminescent solar collectors have an embedded dye with molecules that fluoresce, that give off even more red light.

Example: http://www.soliculture.com/lumo-technology/

Re: Semi-transparent solar panels allow concurrent production of crops and power

#122

Post by samatman » Sun, Aug 23, 2020, 7:18 PM UTC

dehrmann wrote: post #65

khawkins wrote: post #21

Only people who spend most of their life in densely crowded cities could think that the planet has so little space that you'd need to grow crops underneath solar panels for efficiency's sake.

I do worry somewhat about devastating desert ecosystems by paving over them with PV panels, but we're so far from that being a problem right now.

Depends on the desert ecosystem.

Most desert ecosystems have a wretched excess of sunlight, and lack moisture.

Solar panels treat both of these: they capture a lot (but by no means all) of the sunlight, and serve as a nice, concentrated condensing surface for dews.

You can see this at a panel farm in dry areas: there's often a nice row of green in front of each panel, precisely where the condensing dew drips off them onto the ground below.

Re: Semi-transparent solar panels allow concurrent production of crops and power

#123

Post by vmception » Sun, Aug 23, 2020, 7:19 PM UTC

pjc50 wrote: post #109

vmception wrote: post #104

Earlier quoted context omitted.

I'm thinking 3 months would be ideal

Very few things have a return that quickly. In an era of 25 year mortgages, a 10 year payback is very reasonable.

Let's make these one of the few things that have a return that quickly.

Re: Semi-transparent solar panels allow concurrent production of crops and power

#124

Post by bserge » Sun, Aug 23, 2020, 7:22 PM UTC

chrisco255 wrote: post #18

So this technique reduces the sunlight the plants receive by about 57% but only reduces biomass growth by about 30%. It's very interesting. I imagine you could enclose the sides with glass or plastic and make a greenhouse from it. That makes me wonder if the reduction in growth wouldn't be offset by the ability to extend the growing season.

> make a greenhouse from it

That would be literally Earth-saving in some places. I know people who heat their greenhouses with wood! Wood, from forests, which are quickly dwindling, and yet it's cheaper than natural gas, so people use this country's forests to keep warm during winter just because it's cheaper.

From my point of view, that's absolutely insane and this country deserves what it gets.

Which is decreased rainfall, increased summer temperatures, landslides, floods (ironically) and crop damage so bad it puts farmers out of business (they're protesting right now).

Then they wonder "why, God, why?" like a bunch of headless chickens. We deserve everything we get. Sorry, I had to get this off my chest.

Re: Semi-transparent solar panels allow concurrent production of crops and power

#125

Post by samatman » Sun, Aug 23, 2020, 7:24 PM UTC

Retric wrote: post #19

hirundo wrote: post #7

Earlier quoted context omitted.

"if the government were to take over the Sahara Desert, there would be a shortage of sand in five year" -- Milton Friedman (exaggerating, somewhat) Better to put them on home roofs, and arrange for them to be owned by the homeowners, designed so that the occupants are (literally) empowered when the grid is mismanaged, as in California. On highway medians control is more centralized, and they would require more mainte…

Rooftop photovoltaic is currently more expensive, less efficient, and surprisingly dangerous to install. Solar thermal designs actually benefit from being on rooftops. As to dust, economies of scale make a huge difference. It’s rarely worth it, but using a farm truck to spray water across miles of panels is much more efficient than tens of thousands of homeowners doing the same.

It's also unattractive, which should matter to us.

Much of the distinctive beauty of traditional building in sunny areas comes from the roofs.

Solar tiling, which is still not a mature technology, doesn't add danger: we have to put something on a roof, and if installing solar tile takes extra time, it isn't by much. And it looks good.

Less efficient and more expensive? Sure. But as the meme would have it, it's free real estate. And since we're living through a grotesque failure of robustness on a civilizational scale, let me point out that it's more robust as well, particularly combined with on-site batteries.

Re: Semi-transparent solar panels allow concurrent production of crops and power

#126

Post by samatman » Sun, Aug 23, 2020, 7:28 PM UTC

gbrown wrote: post #77

qayxc wrote: post #33

Earlier quoted context omitted.

The setups have to be separate (e.g. different outlets for mains and solar) to protect the grid. Even a small home solar installation puts out enough power to easily kill unsuspecting maintenance personell working on the grid, for example. So the utility company has to have 100% control over he mains at all time for safety reasons (i.e. your meter must never run backwards). If they cut the power (e.g. for maintenance…

That's not true, you can have an inverter setup which fails over to a battery backup when the grid goes down. It's also done all the time with natural gas generators. The setup is more expensive, and it does have to meet certain requirements, but it is definitely an option.

True but, this has been made illegal in many places, California among them.

I don't actually know whether that's legislatively illegal, or simply banned by PG&E; but the effect is much the same.

Re: Semi-transparent solar panels allow concurrent production of crops and power

#127

Post by gdubs » Sun, Aug 23, 2020, 7:32 PM UTC

foolfoolz wrote: post #68

gdubs wrote: post #46

Our area of Oregon recently banned new solar farms on the grounds that it detracts from the beauty of the landscape – a wine region with lots of tourism. Ironically, that very beauty is threatened by the changing climate, which clean energy could help mitigate.

eh i don’t see anything wrong with this. some areas are beautiful and should remain that way. we have a ton of space in oregon and the us. tons of space that no one is ever going to care about. i think it’s ok for people to protect places that have interest and economic benefits

I’m not saying there’s anything wrong with trying to protect the character of the region. In fact, the beauty is something that — hopefully — makes visitors appreciate the environment.

But when you look at what’s already allowed in farm-use zones, there’s plenty of eye-sore potential. So, my issue is with painting with too wide a brush (and unfairly singling out a use that’s arguably important to preserving the environment over the longer term). They should have the ability to look case-by-case.

If someone has an area on their property that’s shielded from public view, why not let them use it for a solar array? Studies have shown that, properly configured, solar arrays can actually improve prairie soils. And like the large array in Hawaii, grazers like sheep can be incorporated into the design.

Just seems bonkers to me to outright ban the solar arrays.

Re: Semi-transparent solar panels allow concurrent production of crops and power

#128

Post by samatman » Sun, Aug 23, 2020, 7:40 PM UTC

manfredo wrote: post #49

christkv wrote: post #38

Earlier quoted context omitted.

Or stacking blocks https://qz.com/1355672/stacking-concrete-blocks-is-a-surpris...

Apparently each of these structures stores 20 MWh of energy. By comparison, the US consumes 11.5 TWh of electricity daily. To reach the 12 hours of storage estimated to be necessary to reach 80% renewable generation we'd need 287,500 of these towers. To reach the 3 weeks of storage necessary for 100% renewable generation we'd need 12,075,000 of these towers.

The former is easily achievable, if the towers are profitable to install. We only have to build them one at a time, and if a collection of 10-50 is cheaper than a peaker gas plant, then the utility decommissions the latter and builds the former.

The latter is simply not necessary. There are a number of ways to solve the last few percent, including leaving a few peaker plants running; presumably, we'll do all of them.

Those peakers can be carbon-neutral, because it's possible to run CO2 extractors. One implication of our renewables is that there are times when they generate power considerably in excess of requirements: using that energy to sequester carbon is plausible.

Of course, if we got over our civilizational horror of nuclear energy, we could solve this problem in a thorough and boring way. I'm not holding my breath.

Re: Semi-transparent solar panels allow concurrent production of crops and power

#129

Post by hellotomyrars » Sun, Aug 23, 2020, 7:40 PM UTC

vmception wrote: post #104

chrisco255 wrote: post #15

Earlier quoted context omitted.

I think we're already there for regular PV. It's getting to the point where a home system will almost pay for itself in less than 10 years.

I'm thinking 3 months would be ideal

Ideal, I guess. Though I don't see how that could ever be possible.

Re: Semi-transparent solar panels allow concurrent production of crops and power

#130

Post by Manfredo_1 » Sun, Aug 23, 2020, 7:41 PM UTC

philipkglass wrote: post #118

manfredo wrote: post #20

Earlier quoted context omitted.

> Batteries are catching up. Are they? The US consumes 11.5TWh of electricity daily. It's estimated that it needs 3 weeks if storage to get to 100% carbon free [1]. By comparison global battery production in 2019 was 300GWh [2]. Even if you factor in the fact that the curve of battery production is rising, it'd take decades to fullfil just the US's storage demands with batteries. There are other storage options like…

The full paper from citation 1 is available here: "Geophysical constraints on the reliability of solar and wind power in the United States" https://escholarship.org/content/qt96315051/qt96315051.pdf If you look at Figure 2, they model different combinations of overproduction, storage, and regional aggregation (interconnection). Overproduction helps significantly. At 50% (1.5x) overproduction, the United States can su…

By comparison, a plant of the same design as the Vogtle plant was built in China at a cost of $7.3B, yielding a cost of $3.17 per watt of output [1] - under 1/3rd of the solar cost with the required overproduction. The Vogtle plant is the first of its kind in the United States. First of a kind plants typically cost about twice as much as subsequent designs.

Furthermore, you're not including the cost of storage for your estimates on solar and wind. Even 12 hours of storage represents a staggering amount of storage - that's 5.75 TWh given the US's average daily 11.5 TWh consumption. Costs per KWh are still on the order of hundreds of dollars per KWh. At $200/KWh 5.75 TWh works out to over a trillion dollars. And this is a recurring cost, as storage needs to be replaced. Hydroelectric storage is cheaper and doesn't need to be replaced, but is geographically limited. Even then, it's not that much cheaper at $100-160/KWh [2]

Yes, renewables work if energy storage becomes effectively free. But energy storage is anything but free.

1. https://en.wikipedia.org/wiki/Sanmen_Nuclear_Power_Station

2. https://www.renewableenergyworld.com/2019/08/08/report-cover....